Prostate cancer may present as a localized tumor or as an aggressive tumor that metastasizes to bone. The molecular that favor prostate cancer osteotropism are not understood, however, recent attention has focused upon bone extracellular matrix proteins because these proteins can elicit cellular proliferation, migration, and adhesion responses. Bone sialoprotein is one extracellular matrix protein that is biologically active toward breast tumor cells and up regulated in breast tumor tissue. Bone sialoprotein is also up regulated in prostate cancer tumors however, the relationship between BSL expression in prostate cancer and the biological effect(s) that this protein has upon prostate cancer is not clear. Given that matrix proteins can alter the biological activity of cells, it is advantageous to characterize the biological responses of prostate cancer cells towards BSP in order to define biological profiles of prostate tumors of prostate tumors. It is anticipated that data collected from this study will augment our ability to discriminate metastatic prostate cancer from non-metastatic prostate cancer. The objective of the proposed study is to determine if bone sialoprotein elicits biological responses in prostate cancer cells. The specific aims of this proposed study include: 1) To characterize the expression of bone sialoprotein in prostate tumor cell lines 2) To determine if bone sialoprotein induces prostatic tumor a) cell proliferation b) cell adhesion and c) cell migration 3) To identify protein domain(s) that induces the cellular response(s).